The book contains circuits that are the best examples of sound frequency power amplifiers made on lamps. With the advent of phonograph records, which began to be made using a special technology, as well as FM broadcasting, the audio signal acquired a better sound quality. In this regard, there was a need for amplifiers that could most accurately reproduce the original signal. This was the reason for the appearance of UMZCH type Hi-Fi.
The authors of the amplifiers described in the book are mainly radio amateurs, but several schemes that were produced on the conveyor are also given. With the modern development of microelectronics, it may seem to many that the use of lamps in the design of amplifiers is a kind of step back into the development of radio electronics. But experienced music lovers still give their preference to tube UMZCH, motivating them with the fact that the “tube” sound is much more pleasant, softer and more transparent.
The author of the collection, tried to preserve the style and text of the description of the original designs, only occasionally added his comments.